The invention is concerned with a pneumatic flat pad with two marginally joined covers of flexible material which form between themselves a hermetically sealed hollow space and are reinforced by cord inserts, and a perforated attachment for connecting the hollow space with a source of compressed air.
As pneumatic lifting devices, particularly for the technical auxiliary service as car jacks and the like, pneumatic flat pads are known which are inflated by means of compressed air and can, while being expanded, perform a lifting operation.
These pads, preferably as flat as possible, are frequently provided with cord inserts for reinforcing the covers. The cord inserts are vulcanized into the covers, which consist of natural or synthetic rubber, in several plies which are always crossed at 90.degree. relative to each other because each cord insert possesses high strength only in one direction and it is intended to achieve by crosswise superposition of the cord inserts the same reinforcing effect in all plane directions of the cover, that is to say, to create isotropic conditions.
Such known pneumatic flat pads have, however, the disadvantage that they can be easily destroyed in the case of higher pressures in the marginal area where the two covers are joined with each other, which brings about a high risk of accidents, not only by the bursting of the pad itself but also by the sudden drop of the propped up load.
The invention has set itself the task to exclude the risk of damage or destruction in the area of the borders existing in the case of the known flat pads of the kind mentioned above.